What are glue records?

Glue records are address records (A or AAAA) provided by the parent zone to help resolvers locate authoritative nameservers when those nameservers are inside the same domain they serve.

They are primarily used for in-bailiwick nameservers, where the nameserver hostname depends on the very zone it is authoritative for.

Without glue, recursive resolvers may not be able to bootstrap resolution for the domain.

• Glue Record Checker

Glue records exist to prevent circular dependencies during DNS resolution.

A resolver may need the IP address of a nameserver before it can query that nameserver, but if that nameserver's address is only available within the same zone, it creates a deadlock.

Glue records break this loop by providing the required address information at the parent level.

Consider a domain like example.com that uses ns1.example.com as its authoritative nameserver.

To query ns1.example.com, a resolver needs its IP address. But if that address is only defined inside example.com, the resolver cannot retrieve it without already reaching the nameserver.

Glue records solve this by publishing the IP address alongside the delegation at the parent zone (such as .com).

Glue is only required for in-bailiwick nameservers, where the nameserver hostname is within the same domain.

• In-bailiwick: ns1.example.com for example.com (requires glue)
• Out-of-bailiwick: ns1.provider.net for example.com (no glue required)

Out-of-bailiwick nameservers can be resolved independently, so no circular dependency exists.

• Whether the nameserver is in-bailiwick
• Whether corresponding A or AAAA records exist at the parent level
• Whether the IP addresses are correct and reachable
• Whether recent DNS or registrar changes have affected delegation

• A records explained
• AAAA records explained

• Missing glue records for in-bailiwick nameservers
• Incorrect IP addresses registered at the parent zone
• Glue not updated after nameserver IP changes
• Registrar configuration not matching zone configuration
• Assuming normal DNS records automatically provide glue

Glue records are not the same as standard A or AAAA records defined within your DNS zone.

They are stored and served by the parent zone (typically managed via your registrar), not within your authoritative DNS zone.

This distinction is important when troubleshooting, as updating your zone file alone may not fix glue-related issues.

If you want to validate this topic in practice, these DNS Pro tools are the fastest next step.

• Glue Record Checker
• Delegation Checker
• NS Lookup